The present invention is drawn to a process for the direct reduction of metal oxides containing iron to a metallized iron product.
The direct reduction of iron oxide, in forms such as pellets or lump ore, to metallic iron in the solid state has become a commercial reality throughout the world in recent years. The combined annual capacity of direct reduction plants currently in operation or under construction is in excess of 15 million metric tons of direct reduced iron product, which is used primarily for feedstock in electric arc steelmaking furnaces. The world demand for additional direct reduced iron is projected to increase at a substantial rate for many years to satisfy a growing world need for such feedstock, as additional electric arc furnace steelmaking plants are constructed.
Known processes for the direct reduction of iron oxide to metallic iron utilize a reformed gas as the reducing agent. Natural gas is used as a source for generating the reformed gas. The reformed gas for use in the direct reduction process is generated in a unit called a reformer by contacting the natural gas with an oxygen containing material in the presence of a catalyst, usually a nickel catalyst, which activates the reformation reaction of the natural gas so as to yield a reformed gas which is rich in H.sub.2 and CO. The reformed gas which is collected from the reformer is thereafter fed to a reduction reactor containing the iron oxide material wherein the direct reduction reaction is carried out. Thus, direct reduction processes heretofore known require two distinct reaction zones for carrying out the actual direct reduction process. In these conventional processes it is required that the reformed gas product in the first zone be treated prior to entering the reduction zone in order to remove CO.sub.2 and/or water vapor.
As noted above, natural gas is used as a source for generating the reformed gas. As natural gas is a valuable natural resource which has many uses, it would be highly beneficial to employ as a source for generating the reformed gas a resource other than natural gas. In particular, it would be highly beneficial to be able to use as a source for generating the reform gas heavy hydrocarbon oils which are readily available. Heretofore it has been impractical to employ heavy hydrocarbon oils in the known conventional direct reduction processes noted above due to the presence of sulfur in the heavy hydrocarbon oil which poisons the catalyst employed in the reformer of the known direct reduction processes. As a result of the foregoing, any prior art process employing heavy hydrocarbon oils required treatment of the heavy hydrocarbon oil to desulfurize the heavy hydrocarbon oil so as to prevent poisoning of the catalyst employed in the reformer of the known direct reduction processes.
Naturally, it would be highly desirable to provide a process which permits the use of heavy hydrocarbon oils having high sulfur contents as a source for generating reformed gas for use in the direct reduction of iron oxides to metallic iron which process does not require prior treatment of the heavy hydrocarbon oil.
Accordingly, it is the principal object of the present invention to provide an improved process for the direct reduction of metal oxides containing iron to a metallized iron product.
It is a particular object of the present invention to provide a process as aforesaid which employs heavy hydrocarbon oil as a natural gas source for generating the reformed gas used in the direct reduction process.
It is a further object of the present invention to provide a process as aforesaid wherein gas reformation and direct reduction of the metal oxides is carried out in a single reaction zone of the direct reduction reactor.
It is a still further object of the present invention to provide a process as aforesaid wherein the DRI material in the single reaction zone of the direct reduction reactor is used as a catalyst to produce a reformed gas directly in the reaction zone which contacts the metal oxides in the reaction zone so as to reduce same to a metallized iron product.
Further objects and advantages of the present invention will appear hereinbelow.